Space Travel

I like math. Or (I should clarify), I like numbers. At higher levels, maths gets all weird and incomprehensible, and that's about the point that I give up. But at lower levels, math is still about the numbers, and so that's what I like.

For sports stuff, I've been reading a lot of Grantland, and they have two guys that do numbers. Bill Barnwell does a good job of breaking down football numbers (and why most teams should go for it on fourth and short. Coaches don't do that often because they're scared of getting fired more than they want to win); while Sebastian Pruiti does incredible things with basketball numbers and graphics. Seriously, I'm there's just a ton of data about how well a players does in specific situations (coming off a pick and roll, taking a pass without a dribble in the post). I knew that there were some numbers like shooting percentages, but the fact they can be broken down so much pretty cool.

Also, I've been playing through the Mass Effect series - partly because it's awesome, but mostly because the next game (Mass Effect 3) comes out on March sixth, and it will undoubtedly blow my mind. I promise these paragraphs have something to do with each other. Honest.

In the Mass Effect universe (it takes place about 170 years in the future), humanity has expanded into the stars and met up with a bunch of alien races. Most technology is based around a weird thing called Element Zero, or Eezo for short. When electricity is passed through Eezo, it changes its mass. I know, that violates at least one law of physics, and probably a few more as well. Sure, it's Applied Phlebotinum, but whatever. Everything else is explained fairly well (and in some depth, too). Anyway, putting Eezo engines on ships and in Mass Relays (huge devices scattered throughout the galaxy) has enabled faster than light travel. We can zip from one side of the galaxy to the other in a few short second.

This is a bit different than the FTL drives in Star Wars and Star Trek. Star Wars has a hyperdrive, which seems to be like the engine in a car. The better then engine, the faster it goes through hyperspace. Star Trek uses Warp Speed, which is based on some sort of logarithmic scale, except that Warp 10 is infinity (or so I heard. It was in Voyager, and I watched that episode a long time ago and didn't pay too much attention).

These three universes all tend to portray FTL travel as normal, which is fine as long as you work out the physics. And control gravity. See, to get up to lightspeed, you'd need to accelerate to lightspeed. Do you know how long that would take? Sure, you could go from zero to lightspeed in a matter of seconds, but your crew would be red smears on the back of your ship, which may or may not have survived the stresses. The human body can only survive so much acceleration before it gives up and dies. Most fictional universes have some sort of inertial compensator (both Star Wars and the Honor Harrington universe both explicitly mention these), but in real life, we don't.

Imagine for a moment that lightspeed was no barrier, but all other physics were in place. That we could go as fast as we wanted, provided we could get achieve that velocity conventionally. Alpha Centauri is roughly four light years away. To get there, we'd need to accelerate until we were halfway there, and then turn the ship around and start to brake.

That is, unless you put engines on the front of your ship as well. And designed the interior ceilings to also be floors (and vice-versa). Acceleration would provide the gravity. I'm just going to go ahead and ignore the nearly-weightless part where we turn the ship around, because it would play havoc with whatever direction we wanted our feet to go (for instance, unless it was a carefully controlled burn centered around a point in front of the ship, the gravity would vary wildly depending on where in the ship you were).

Now, I'm going to go ahead and say that we'd want gravity on our ship to be the same on earth, so we'd be accelerating at 9.81 m/s² until we had to turn around. At that rate, it would take about 4 years to get to Alpha Centauri. It's 4 lightyears away, and it takes quite a while to get there, even with constant acceleration (by the way, our velocity when we turned around would be a little over twice the speed of light). Even if we got up to two gravities of acceleration, it would still take about 2 years and 9 months to get there. Time is inversely proportional to the square root of acceleration, so to cut the time in half, we'd have to quadruple the acceleration. It would still take us two years to get there at four gravities, and I'd hate to think of the effect that would have on our bodies. Two years at four times our weight? We'd be dead when we got there.

Here's a picture of the nearest stars to earth. In a 15 light year radius, there are a number of stars. Of course, to go 15 light years safely (accel of one gravity) would take 7.6 years. We could colonize it, but trade? Impossible. And since information would either be passed by light (15 years), or by ship (~7.5 years), communication would be next to impossible.

Our galaxy is around 110,000 light years across. To cross it safely would take over 650 years! If galactic space travel were possible, it's not the velocity that would kill exploration. It's the acceleration.